Can the headlamps(vs. the entire headlight unit)be easily replaced on a '91 911? on 1991 Porsche 911

I'm looking to replace the lamps (internal to the headlight unit) only, not the entire headlight unit

Asked by for the 1991 Porsche 911
This video should help you http://www.youtube.com/watch?v=D65x8G1f6AI
Thanks, but on my '91 911 the rubber plug on the trunk sidewall appears to be sealed. Do I need to push through this somehow?
1 more answer , 1 more comment
Wow, this headlight unit must be the EASIEST one to replace...
OK. Now how?